The invention relates to a grid girder for raised floors, comprising legs which incorporate cover plates for connection and attachment of the grid girders which are manufactured of square pipes, as well as floorboards or tiles laid out on the grid girders, and the cover plates of the legs are provided with pairs of recesses arranged around their peripheries in the form of a cross and boreholes to receive either the grid girder ends or else tongues, taper plugs or fastening screws mounted on the ends of the grid girders.
In order to strengthen the supporting substructure of raised floors, it is known to mount grid girders between the cover plates of the legs, on which the floorboards or tiles are then laid out. The cover plates of the legs for this purpose have pairs of recesses arranged in a cross-like configuration around their periphery, into which the side walls are inserted from above at the ends of each grid girder. One of the two other walls of the grid girder is provided with corresponding recesses at its ends, in order to facilitate the introduction of the ends of the side walls of the grid girder into the recesses in the cover plates of the legs. On the wall-end segments of the grid girders lying opposite and facing these recesses are provided inward projecting tongues, with one type of girder, and boreholes, with another type of girder, instead of these tongues, and the boreholes are arranged for the introduction of fastening screws. The grid girders with tongues at their ends are inserted practically speaking loosely into the supporting substructure, while the other grid girder type is screwed into the cover plates of the legs. In the just cited case the supporting substructure obtains a further improved reinforcement. The two different reinforcement modifications which have been applied to the supporting substructure of the raised floor until this time however, have required the production and warehousing of two different types of grid girders, which is a practical disadvantage. It then happens that sharp edges are present on the elements, as a result of the aforementioned recesses in the ends of the grid girder, which with the assembly of raised floors and also with subsequent installation procedures form a danger of injury to the assemblers.